America's top military officer General Martin Dempsey has already seen one Middle Eastern civil war. He is much more cautious about involvement in another.
While Dempsey, 61, has argued in favor of the White House's idea of limited military strikes against Syria and arming moderate rebels, he has made clear his lack of enthusiasm for widening America's role in the conflict much beyond that.
A decade ago, Dempsey was a brigadier general commanding the 1st Armored Division in Baghdad. The United States had toppled President Saddam Hussein, expecting to bring stability to Iraq. But Iraqi insurgents took advantage of a power vacuum to launch a bombing campaign that targeted mosques, hotels and embassies - including a blast that killed the U.N. envoy.
Dempsey acknowledged in 2011, the year he was appointed chairman of the Joint Chiefs of Staff, that U.S. political and military leaders - including himself - had failed to fully grasp the strength of sectarian hatreds in Iraq.
"I didn't understand the dynamic inside that country, particularly with regard to the various sects of Islam that fundamentally, on occasion, compete with each other for dominance," he told a hearing in the U.S. Congress.
"I've reflected about that a lot," he said. "I've learned that issues don't exist in isolation. They're always complex," said Dempsey, who has been criticized by Republican Senator John McCain for not pushing harder for military action in Syria.
The chance of a U.S. attack has lessened in recent days as Washington and Moscow explore a way to secure Syria's chemical weapons, but Obama told Americans in a televised address on Tuesday that he is ready to use force if the diplomacy fails.
Dempsey has warned against setting up a no-fly zone or U.S. intervention that would change the course of the civil war and lead to the collapse of the Syrian government without a clear understanding of what might follow.
In Iraq, Dempsey's division was the biggest single U.S. military element at the time, and he frequently went out onto the streets of Baghdad.
"General Dempsey realized early on that there were going to be issues developing institutions and stable governance in post-Saddam Iraq," said Lieutenant Colonel David Gercken, who served with him in Iraq.
Dempsey's forces had their tour of duty extended to deal with rising violence from the followers of Shi'ite militia leader Moqtada al-Sadr.
He left Iraq after 14 months and returned in August 2005 for a two-year tour as head of an effort to train Iraqi security forces to handle their own national security.
That was the height of the sectarian war that ripped the country apart as Shi'ite militias and death squads as well as Sunni groups linked to al Qaeda slaughtered thousands of people. Mosques, including one of the holiest sites in Shi'ite Islam, were bombed and desecrated.
Dempsey belongs to a cadre of warrior scholars who have inhabited the upper ranks of the U.S. military in recent years. Two others are Admiral James Stavridis, who became dean of the Fletcher School of Law and Diplomacy at Tufts University after retiring from the military this year, and retired Army General David Petraeus, who has a doctorate from Princeton.
Dempsey, who holds a master's degree in English from Duke University focusing on Irish literary figures, said Iraq had made him ponder America's haste to use military force.
"I've been scarred by rereading a quote from Einstein, who said if you have an hour to save the world, spend 55 minutes of it understanding the problem and five minutes of it trying to solve it," he told lawmakers two years ago.
"I think sometimes, in particular as a military culture, we don't have that ratio right," Dempsey said. "We tend to spend 55 minutes trying to ... solve the problem and five minutes understanding it."
His approach to Syria has aroused the ire of critics who have pushed for quick, decisive U.S. action to help the collection of rebel groups fighting to oust Assad.
McCain said in June that the "situation is much more dire than it was" when Dempsey became chairman and suggested that U.S. "inaction" had created an even greater threat to American national security interests.
"You say ... we need to understand what the peace will look like before we start the war," said McCain to Dempsey, noting the rising death toll in Syria. "Do you think we ought to see how we could stop the war by intervening and stopping the massacre?"
Others have joined the chorus. Retired Major General Robert Scales, a former commandant of the U.S. Army War College, wrote in The Washington Post that the chairman's "body language" at recent congressional hearings about whether to attack Syria for its alleged use of chemical weapons made it clear that he "doesn't want this war."
Supporters say, unlike Secretary of State John Kerry who has led the push for action against Syria, the chairman of the Joint Chiefs, out of respect for civilian control of the military, has to walk a fine line between advice and advocacy.
"What McCain was asking Dempsey to do was to make a choice about what's in the best interests of the United States. That is a policy ... choice that is not the role of the chairman," said Richard Kohn, a professor emeritus at the University of North Carolina who has studied civilian control of the military.
"We have a long tradition of the proper norms and behaviors of the most senior military adviser to the president of the United States," said Kohn, who has advised Dempsey. "It is definitely not his role to be pushing the president to be doing anything in particular."
(Editing by Alistair Bell, Peter Henderson and Christopher Wilson)